kenel Posted July 15, 2002 Share Posted July 15, 2002 Is anyone willing to explain who inveted the parsec unit, and why it is used? 3.26163388338 Light Years...why not use light years? I understand it is a valuable unit of measurement for long distances, but I would like to know more about who invented it, and why it was invented. Link to comment Share on other sites More sharing options...
fafalone Posted July 15, 2002 Share Posted July 15, 2002 Parsec is short for parallax second, it operates on the principle of using your position and the position of a known object to calculate the distance from an unknown object. a "second" is a degree measurement (degree, minute, second). Not sure of the exact reason for it's use, but I'd guess because its closer to expressing how distance is actually measured, since we can't directly measure how long light traveled. It's most commonely used in describing huge distances, like the nearest galaxy is about 7Mpc away (megaparsecs). I don't know the history of it offhand, I'll get back to you. Link to comment Share on other sites More sharing options...
Radical Edward Posted July 19, 2002 Share Posted July 19, 2002 it's a convenient label. I'll let fafalone explain it tomorrow as I can't be arsed right now. sorry Link to comment Share on other sites More sharing options...
DocBill Posted March 18, 2003 Share Posted March 18, 2003 Originally posted by Radical Edward it's a convenient label. I'll let fafalone explain it tomorrow as I can't be arsed right now. sorry Simply put, the Light Year is fine for very short distances. However, when meassuring the vissiblke universe, the number of light years becomes ungainly. It is much easier to meassure in Mega Parsecs (Mpc) than in billions and billions of LY's. Bill Link to comment Share on other sites More sharing options...
Guest NuHertz Posted March 19, 2003 Share Posted March 19, 2003 Originally posted by DocBill Simply put, the Light Year is fine for very short distances. However, when meassuring the vissiblke universe, the number of light years becomes ungainly. It is much easier to meassure in Mega Parsecs (Mpc) than in billions and billions of LY's. Bill Yes, but, why 3.26163388338 light years? I see it as a tool for somewhat larger distances, but, where did it arise? How was it calculated? I see its use but not how it was derived. Link to comment Share on other sites More sharing options...
JaKiri Posted March 21, 2003 Share Posted March 21, 2003 Originally posted by NuHertz Yes, but, why 3.26163388338 light years? I see it as a tool for somewhat larger distances, but, where did it arise? How was it calculated? I see its use but not how it was derived. A parsec is the distance at which 1 AU (astronomical unit, basically the distance from the earth to the sun) subtends (is the straight line distance between, ie. not on the arc) one arc second. Or in other words, think of a big isosceles wedge, with the unique angle being 1/3600th of a degree. If 1AU is the length of the side opposite this angle, then one parsec is the length of the other 2 sides. The value came about due to measuring the distances of stars by the parallax caused by the movement of the earth in its orbit. If memory serves, one parsec represents a practical rather than a theoretical maximum on this technique. Link to comment Share on other sites More sharing options...
Radical Edward Posted March 21, 2003 Share Posted March 21, 2003 it is just another unit. Astronomers and cosmologists had to invent something so that they could feel special, since they don't have anything of their own. Link to comment Share on other sites More sharing options...
JaKiri Posted March 21, 2003 Share Posted March 21, 2003 Originally posted by Radical Edward it is just another unit. Astronomers and cosmologists had to invent something so that they could feel special, since they don't have anything of their own. Originally not (see post), but effectively now it is. Link to comment Share on other sites More sharing options...
Radical Edward Posted March 21, 2003 Share Posted March 21, 2003 I know though to them it does represent quite a nice number in terms of angles and things. I'll let them off, poor little mites. Link to comment Share on other sites More sharing options...
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